1. Field
One or more embodiments relate to a thermoelectric material, and a thermoelectric element and a thermoelectric module including the thermoelectric material, and more particularly, to a thermoelectric material having excellent thermoelectric properties by irradiating the thermoelectric material with energetic particles such as protons, neutrons, or ion beams, and a thermoelectric element and a thermoelectric module including the thermoelectric material.
2. Description of the Related Art
In general, thermoelectric materials are used in active cooling, waste heat power generation, and like applications by taking advantage of the Peltier effect and the Seebeck effect. FIG. 1 schematically illustrates thermoelectric cooling using the Peltier effect in which a voltage is applied through electrical contacts 111, 112 across a structure of p-type thermoelectric material 121 and a structure of n-type thermoelectric material 122 arrayed parallel to one another and connected by a conductor 130. As illustrated in FIG. 1, the Peltier effect is demonstrated when the external DC voltage is applied across the p- and n-type thermoelectric materials 121 and 122, respectively, holes generated in the p-type material and electrons generated in the n-type material are transported (i.e., flow) in the same direction toward the heat generating end (small arrows) away from a region of heat absorption, and toward a region of heat generation located at opposite ends of both the p-type and n-type materials structures. FIG. 2 schematically illustrates thermoelectric power generation by the Seebeck effect. Referring to FIG. 2, the Seebeck effect is demonstrated when heat supplied from an external heat source 230 to a p-type thermoelectric material 221 and an n-type material 222, induces a flow of current generated in the p-type thermoelectric material 221 (holes) and the n-type thermoelectric material 222 (electrons) where the electrons and holes are transported away from the heat source 230 through the thermoelectric materials 221 and 222 and through electrical contacts 211 and 212, thereby generating power (current flow shown by arrow (I)).
Active cooling that employs a device fabricated from a thermoelectric material improves the thermal stability of devices, does not cause vibration and noise as would accompany, for example, a heat sink and fan combination, and does not use a separate condenser and refrigerant, and thus the volume of devices is small and the active cooling method is environmentally-friendly. Thus, the active cooling by a device that uses such a thermoelectric material may be applied to refrigerant-free refrigerators, air conditioners, a variety of micro-cooling systems, and the like. In particular, when a thermoelectric device is attached to, for example, a memory device, the temperature of the memory devices may be reduced and maintained at a uniform and stable temperature, in comparison with a conventional cooling method which has greater variation in temperature across the cooling apparatus. Thus, the performance of, for example, memory devices may be improved.
Meanwhile, when thermoelectric materials are used for thermoelectric power generation by using the Seebeck effect, the waste heat extracted thereby may be used as an energy source. Thus, thermoelectric materials may be applied in a variety of fields that increase energy efficiency or reuse waste heat, such as in vehicle engines and air exhausts, waste incinerators, waste heat from smelters such as in iron mills, power sources for medical devices for the human body which use human body heat, and the like.
As a factor determining the performance of such thermoelectric materials, a dimensionless figure-of-merit ZT defined in Equation 1 below is used.
                    ZT        =                                            S              2                        ⁢            σ            ⁢                                                  ⁢            T                    k                                    Equation        ⁢                                  ⁢        1            
In Equation 1, S is a Seebeck coefficient, a is electrical conductivity, T is absolute temperature, and K is thermal conductivity.